It is an object of the invention to provide an actuation device for an explosion proof housing that is adapted for more reliable operation and cost effective implementation.
The actuation device comprises a mechanical actuation unit with a first carrier. An actuating element is supported by the first carrier so as to be movable in axial direction relative to said first carrier. The actuation element can be moved in axial direction by a push-button or a push-key. Alternatively, the actuation unit may comprise a rotary switch or turnkey. Its rotary motion can be translated into an axial motion by a transmission. The transmission may be a cam, a tapered land arrangement or the like. Due to an inclined surface opposite the axial direction as well as an inclined surface in the direction of rotation, it is possible to generate an axial movement of the actuation element.
The actuation device further comprises a switch unit. The switch unit has a second carrier on which is arranged at least one switch element that can be moved in axial direction. When installed, the switch unit is located in the interior of the explosion-proof housing. For example, the switch unit may be an electrical or electromechanical switch that may act as the ignition source and thus is also accommodated in the housing. In an assembled operative state, the actuation unit is located outside the interior of the housing.
Furthermore, the actuation device comprises an adapter device with an adapter body. The adapter body extends in axial direction, in which case it extends through the housing wall in an assembled operative position. On its one axial end, the adapter body has a first mounting section and, on its opposite other axial end, it has a second mounting section. At least one adapter channel extends in axial direction in the adapter body, in which case, in each channel an adapter plunger is supported as to be movable in axial direction. The number of adapter plungers corresponds to the number of switch elements or switch positions of the switch unit that are to be actuated. There may be one, two or even more switch elements or switch positions and a corresponding number of adapter plungers. If two or more adapter plungers are provided, the plunger channels extend parallel to each other and, in particular, along a longitudinal axis extending at a distance from the axial direction through the adapter body. A gap resistant to ignition is formed at least in one axial section between each adapter plunger and the associate adapter channel. As a result of this, it is ensured that there will be no ignition starting in the housing interior and moving through the at least one adapter channel into a potentially explosive atmosphere.
In a preferred embodiment, the at least one adapter plunger is pretensioned in a starting position toward the actuation unit or the actuation element by means of a pretensioning means, for example a spring, preferably a helical spring. By means of the actuation element, the adapter plunger can be moved or slid in axial direction out of its starting position. A rotary motion of the adapter plunger about its longitudinal axis or about the axial direction is not caused by the at least one actuation element. Each adapter plunger has a first axial end that is associated with the at least one actuation element. The opposite axial second end of each adapter plunger is associated with a respective switch element of the switch unit. In each instance, it is, preferably, only pressure forces acting in axial direction that are transmitted between the at least one adapter plunger and the actuation element on the first end, as well as between the adapter plunger and the switch element on the second end. To accomplish this, for example, the adapter plunger may have a first plunger face on its first end and a second plunger face on its second end. The plunger face of the first plunger end abuts loosely and without positively locking against the associate actuation element. Conversely, the second plunger face of the adapter plunger can abut loosely and without positively locking against the associate switch element of the switch unit. Preferably, the at least one adapter plunger extends straight along one axis.
The first carrier of the actuation unit is separably connected to the first mounting section, and the second carrier of the switch unit is separably connected to the second actuation section of the adapter device. Consequently, the adapter body acts, at the same time, as the carrier for the actuation unit and for the switch unit. An assembly unit is created. In doing so, the first carrier and the second carrier are immovably arranged on the adapter body.
Adjoining the at least one adapter plunger the transmission means for translating a rotary motion of an actuation element into an axial motion can be arranged in the region of the first mounting section. The transmission means can be associated with the adapter device as an optimal assembly or be a component of the actuation unit.
The two mounting sections on the adapter body between which extends the at least one adapter plunger thus act as mounting section locations for the actuation unit, with or without transmission, on the one hand, and for the switch unit, on the other hand. It is only the adapter device that must satisfy the requirements of an embodiment that is resistant to ignition transmission and that is accordingly tested and certified, respectively. The actuation unit and the switch unit that are used may be standard assemblies. This has the advantage that the use of different actuation units and/or switch units for different applications in combination with always the same tested adapter device is possible. A test for protection against explosion and certification of the entire actuation device for each and every application can thus be omitted. It is sufficient if the adapter device that is used is tested once to satisfy the requirements. Considering different applications, the standard components can be mounted to the adapter device, thus requiring considerably less work and considerably lowering costs.
As a result of the fact that the actuation unit, the adapter device and the switch unit are directly arranged next to each other in a separable manner, a safe operation of the switch unit via the actuation unit is ensured at all times. Even when axial pulling forces are exerted on the actuation unit, the at least one adapter plunger will not move away from the associate switch element in a manner that a safe actuation of the switch element via the actuation unit is no longer ensured.
In one exemplary embodiment the adapter device comprises a first mounting device, by means of which the first mounting section of the adapter body is separably connected to the actuation unit. Additionally or alternatively, the adapter device may comprise a second mounting device by means of which the second mounting section of the adapter body is separably connected to the switch unit. Via the first and/or second mounting devices, preferably a positive-locking and/or a nonpositive-locking connection is established, for example a screw connection and/or click-on connection.
In one advantageous exemplary embodiment, the first mounting device comprises a connecting part arranged or held on the actuation unit. The connection part is connected in a positive-locking or a nonpositive-locking manner to the first mounting section of the adapter body in order to establish the separable connection. For example, the connection part may have a thread that comes into engagement with the corresponding counter-thread on the first mounting section. In one exemplary embodiment the connection part is provided with an inside thread that can be separably connected to the outside thread on the first mounting section. In doing so, the connection part represents a union nut. In one exemplary embodiment the first mounting section may be configured as a hollow cylinder.
The connection part can be separably held on the actuation unit by a holding part. For example, the holding part may come into nonpositive and/or positive engagement with a recess on the actuation unit and act as a stop or as a safeguard against loss for the connection part. The arrangement of the holding part and thus the connection part on the actuation unit preferably does not require any tools.
At least at one point, the holding part may be in contact with the first mounting section of the adapter body. As a result of this, the holding part and the first mounting section, together, can form a rotary position setting means. By means of the rotational position presetting means, it is possible to preset the relative rotary position about the axial direction or about the longitudinal axis of the adapter body between the actuation unit and/or the actuation element and/or the first carrier, on the one hand, and the adapter body, on the other hand. Consequently, it is ensured that a desired allocation of the actuation element to the at least one adapter plunger is ensured and that the actuation of the actuation element is safely accomplished via the adapter plunger in view of the associate switch element.
In one embodiment, the adapter body may additionally have a center section having preferably a cylindrical exterior contour. The at least one adapter plunger is supported on or in this center section, or the at least one adapter channel is provided.
Preferably, the actuation unit comprises no electrical or electronic components whatsoever but consists only of mechanical elements that cannot act as an ignition source. Inasmuch as the switch unit is arranged inside the explosion-proof housing, there are no demands made on the switch unit with regard to explosion protection. If the actuation unit comprises components that could act as ignition source, it is advantageous if the actuation unit is configured in compliance with the ignition protection category “increased safety”.
In operative mode, the adapter body extends through a preferably essentially cylindrical opening in the housing wall. Between the housing wall and the adapter body, there is a gap resistant to ignition transmission. This gap that is resistant to ignition transmission can be configured as a cylindrical gap without profile, as a gap with a profile or as a threaded gap with an explosion-proof thread.
Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings, in which:
While the invention is susceptible of various modifications and alternative constructions, certain illustrative embodiments thereof have been shown in the drawings and will be described below in detail. It should be understood, however, that there is no intention to limit the invention to the specific forms disclosed, but on the contrary, the intention is to cover all modifications, alternative constructions, and equivalents falling within the spirit and scope of the invention.